Spark plug with anti-fouling means and fixed spark gap



Jan. 24, 1967 B. c` FISHER SPARK PLUG WH ANTFOULNG MEANS AND FIXED SPARKGAP F11ed Ma 27, 1963 the passage around the threads during the intakestroke cls the entire device and supplies the region around theelectrodes With fresh ail Which iS forced int0 the Space around theinsulator and the Wer portion of the shell with the incoming fue1mixture to provide a highly coInbustible mixture vvhich insures easystarting and very smooth idling I have found that exceuent results areproduced vvhen the dinlensions of the parts adjacent the sparkingelectrodes are as follovvs:

Diameter of bore 11 --Inches 28S to .290 Iength of bore 11 includingShoulder 2 and pr0jections 35 Inches-- .432 t0 .437 Diameter ofij1sulator portion l8 d0 .235 t0 '240 Length of insulator portion 18 d0.120 to 1ZS Diameter of insulator portion 18 d0 'Z3S t0 .240 Length ofinsulator portion 18 do .120 to 12S Diameter of insulator p01tion l -d0.200 to .20 Iength of insulat0r ortion l ----d0 10 to 1S outsidediameter of Split tube electrode 34 dO 12 Inside diameter of electrode34 d0 07 l)istance betvveen end of projections 35 and insulator Inches.030 to .040 Taper of end Of She11 and projections 35 30 I have foundthat when the tllbe 34 iS made of nickel and the shell is made ofnon-0xidizing cold rolled Steel, such aS that knovvn as "C R.S. BIII3the Surfaces of the electrodes do not 0Xidize and T10 high fesistancefor the Spark iS built up at these Surfaces. Hence a Spark iS roduced ata v01tage n1uch lowel than that required fol' an ofdinary spark plug.Tests show that the spark OC curs at 4,000 V0lts, leaving a voltagereserve in the coil at all load requiren1ents There is thus almost n0excess heat generated by high cufrent in the device or the aSSO- ciatedignition circuit, and an infa11ible spark is produced at aTly enginespeed vvhile One en1b0dinent of the invention has been Shown anddescribed, various m0difications may be nade in the arrangement of theparts and in the geometry there0f, and I do not therefofe Wish t0 liInitTny invention to vvhat has been shown and described, except as Suchlimitations occur in the appended caim' vvhat I desire t0 claim andSecure by Letters Patent is:

An ignition device for an internal combustion engine comprising:

(a) a tubular Shell having a body p0rtion and a threaded portion ofSmaller cross section than said body p0rtion for attaching said deviceto an engine block, said She11 having a first cylindrical bore throughthe threaded portion there0f and a Second cylindrical bore of largerdiarneter than said TSt bore vvithin Said body portion and provid ng atapered shoulder between the tw0 bores,

(b) an insulator extending through Said Shell With one end of saidinsulat0r tern1inating near the end of the threaded portion of saidshell and the other end of said insulator extending out of said bodyportion, said insulat01 Within said second boIe of Said Shell having adian1eter to iit easily Within said Second bore and the portion of saidinsulator vvithin Said first bore having three ortions of SuccessivelydecreaSing diameters providing Successively greater distances betweenthe inner vvall of aid Shell and said insulator tovvards said one end ofsaid insulator, said insulator having a tapered Shoulder between thelargest of said laSt-mentioned portonS and the portion of said insulatorvvithin sai(1`second bore, the taper of Said shoulder beingsubstantially the sanle as that of said tapered shoulder in Said Shell,the portions of successively decreasing diameters having shouldersbetween them With Sharp edges,

(c) a. conductor extending through Said insulator,

(d) a cup-Shaped electrode set into said one end Of said insulator andin contact vvith said conductor, vvith the end of said electrodesubstantia11y uSh With the end of said insulator,

(e) means for providing a gastight connection between said Shell andsaid insulator,

(f) a Shoulder on the 0uter Sufface between Said body portion of saidshell and said threaded ortion, Said shoulder lying in a planeperpendicular to the axis of Said shen,

(g) a groove in said Shoulder,

(h) at least one aperture betvveen the outer Surface Of said bodyportion and Said groove, said grove being located S0 as to provide ac0mmunication between said gr00ve and the helical passage around Saidthreads vvhen Said device is Secured in place in an engine b10ck, and

(i) at least one inwardly extending projection froln the end of saidthreaded ortion of said she11 and tefminating appr0ximately .03 inchfrom the end of said insulator containing said cup-Shaped elec trode,the edges 0f said invvardly extending projections Which are towards theadjacent end of Said Shell being uSh axiauy With the end of saidinsulator and the app[0xi!nate spacing of the three portions ofs11ccessive1y decreasing diameters of Said insulator from said Shellbeing respectively .010 .00, and '080 inch References Cited by tleExalniner UNITED STATES PATENTS l,z16,l39 z/1917 Kopl 313143 1,37,10/192 vv00dr00f 313137 Z,S9l,718 4/1952 Paul 313 x 2,899 8 8/199DOllnbeTg 313130 x 3 012 084 12/196l Fisher. 3,016,4ll l/l962 Fisher313llj FOREIGN PATENTS 344,j7l 3/ 1931 (...Teat Bitain

